A study of species containing Si-O bonds in low temperature matrices and in the gas phase

The work conducted for this thesis involved investigating reactions of species containing Si-O bonds. Various cyclic and linear siloxanes were pyrolysed in an attempt to isolate and identify dimethylsilanone (Me2Si=0) - a molecule of fundamental importance in silicone chemistry. It was observed that these experiments produced products such as CH4, C2H2, C2H4 and C2H6, as well as the methyl radical. It was also seen that both octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane produce bands due to hexamethylcyclotrisiloxane. This suggested that interconversion reactions were occurring upon pyrolysis, indicating the involvement of dimethylsilanone. It was also found that 1,1,3,3,5,5-hexamethyltrisiloxane and 3H, 5H-octamethyltetrasiloxane was not observed upon pyrolysing any of the two sets of siloxanes. The reactions of species producing compounds containing Si-O bonds were also studied. Silylene was reacted with oxygen, nitric oxide and oxetane and the reactions followed using the technique of Laser Resonance Absorption Flash Kinetics Spectroscopy. In both cases, ah initio and semi-emperical calculations were carried out in order to help understand the reaction pathways occurring. As a result of a number of energy and frequency calculations, the most feasible products and in some cases mechanisms, were able to be deduced.